This invention relates to a code-scanning system for acquiring and processing information that is stored in an array of width coded lines printed on a label or the like. In reading code formats of this kind, a light sensitive or photo-responsive device produces electrical signals that correspond to the relative intesities and duration of the light that is reflected from the sequence of lines and spaces.
In these systems, the amplified output signal, if not gain controlled, can be noisy (i.e. generate stray electrical signals) and the output amplifier requires a larger dynamic range amplifier for the output signal which will necessarily be required because of these input signals. Typical of the factors that can lead to excessive voltage range and possibly inadequate signals are:
A. Variation in the pen angle relative to the coded surface; PA1 B. Changes in light source intensity and photodetector sensitivity; PA1 C. Variations in label reflectivity; PA1 D. Variations in print contrast; PA1 E. Differences in amplifier gain characteristics.
In spite of the need to provide an automatic self-adjustment feature in these code scanning systems, a fully acceptable technique for stabilizing the peak-to-peak voltage output from the linear amplifiers that process the input signals has not been suggested.
Clearly, there is a need to provide some means for regulating the amplified output signal from these systems to function within a predetermined voltage range in spite of almost unpredictable fluctuations in the character of the light that is reflected from the labels.